259 lines
6.8 KiB
Groff
259 lines
6.8 KiB
Groff
.\" Copyright (c) 1991, 1993
|
|
.\" The Regents of the University of California. All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 3. All advertising materials mentioning features or use of this software
|
|
.\" must display the following acknowledgement:
|
|
.\" This product includes software developed by the University of
|
|
.\" California, Berkeley and its contributors.
|
|
.\" 4. Neither the name of the University nor the names of its contributors
|
|
.\" may be used to endorse or promote products derived from this software
|
|
.\" without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" @(#)exec.3 8.3 (Berkeley) 1/24/94
|
|
.\"
|
|
.Dd January 24, 1994
|
|
.Dt EXEC 3
|
|
.Os
|
|
.Sh NAME
|
|
.Nm execl ,
|
|
.Nm execlp ,
|
|
.Nm execle ,
|
|
.Nm exect ,
|
|
.Nm execv ,
|
|
.Nm execvp
|
|
.Nd execute a file
|
|
.Sh SYNOPSIS
|
|
.Fd #include <unistd.h>
|
|
.Vt extern char **environ;
|
|
.Ft int
|
|
.Fn execl "const char *path" "const char *arg" ...
|
|
.Ft int
|
|
.Fn execlp "const char *file" "const char *arg" ...
|
|
.Ft int
|
|
.Fn execle "const char *path" "const char *arg" ... "char *const envp[]"
|
|
.Ft int
|
|
.Fn exect "const char *path" "char *const argv[]" "char *const envp[]"
|
|
.Ft int
|
|
.Fn execv "const char *path" "char *const argv[]"
|
|
.Ft int
|
|
.Fn execvp "const char *file" "char *const argv[]"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm exec
|
|
family of functions replaces the current process image with a
|
|
new process image.
|
|
The functions described in this manual page are front-ends for the function
|
|
.Xr execve 2 .
|
|
(See the manual page for
|
|
.Xr execve
|
|
for detailed information about the replacement of the current process.)
|
|
.Pp
|
|
The initial argument for these functions is the pathname of a file which
|
|
is to be executed.
|
|
.Pp
|
|
The
|
|
.Fa "const char *arg"
|
|
and subsequent ellipses in the
|
|
.Fn execl ,
|
|
.Fn execlp ,
|
|
and
|
|
.Fn execle
|
|
functions can be thought of as
|
|
.Em arg0 ,
|
|
.Em arg1 ,
|
|
\&...,
|
|
.Em argn .
|
|
Together they describe a list of one or more pointers to null-terminated
|
|
strings that represent the argument list available to the executed program.
|
|
The first argument, by convention, should point to the file name associated
|
|
with the file being executed.
|
|
The list of arguments
|
|
.Em must
|
|
be terminated by a
|
|
.Dv NULL
|
|
pointer.
|
|
.Pp
|
|
The
|
|
.Fn exect ,
|
|
.Fn execv ,
|
|
and
|
|
.Fn execvp
|
|
functions provide an array of pointers to null-terminated strings that
|
|
represent the argument list available to the new program.
|
|
The first argument, by convention, should point to the file name associated
|
|
with the file begin executed.
|
|
The array of pointers
|
|
.Sy must
|
|
be terminated by a
|
|
.Dv NULL
|
|
pointer.
|
|
.Pp
|
|
The
|
|
.Fn execle
|
|
and
|
|
.Fn exect
|
|
functions also specify the environment of the executed process by following
|
|
the
|
|
.Dv NULL
|
|
pointer that terminates the list of arguments in the parameter list
|
|
or the pointer to the argv array with an additional parameter.
|
|
This additional parameter is an array of pointers to null-terminated strings
|
|
and
|
|
.Em must
|
|
be terminated by a
|
|
.Dv NULL
|
|
pointer.
|
|
The other functions take the environment for the new process image from the
|
|
external variable
|
|
.Va environ
|
|
in the current process.
|
|
.Pp
|
|
Some of these functions have special semantics.
|
|
.Pp
|
|
The functions
|
|
.Fn execlp
|
|
and
|
|
.Fn execvp
|
|
will duplicate the actions of the shell in searching for an executable file
|
|
if the specified file name does not contain a slash
|
|
.Dq Li /
|
|
character.
|
|
The search path is the path specified in the environment by
|
|
.Dq Ev PATH
|
|
variable.
|
|
If this variable isn't specified, the default path
|
|
.Dq Ev /bin:/usr/bin:
|
|
is
|
|
used.
|
|
In addition, certain errors are treated specially.
|
|
.Pp
|
|
If permission is denied for a file (the attempted
|
|
.Xr execve
|
|
returned
|
|
.Er EACCES ) ,
|
|
these functions will continue searching the rest of
|
|
the search path.
|
|
If no other file is found, however, they will return with the global variable
|
|
.Va errno
|
|
set to
|
|
.Er EACCES .
|
|
.Pp
|
|
If the header of a file isn't recognized (the attempted
|
|
.Xr execve
|
|
returned
|
|
.Er ENOEXEC ) ,
|
|
these functions will execute the shell with the path of
|
|
the file as its first argument.
|
|
(If this attempt fails, no further searching is done.)
|
|
.Pp
|
|
If the file is currently busy (the attempted
|
|
.Xr execve
|
|
returned
|
|
.Er ETXTBUSY ) ,
|
|
these functions will sleep for several seconds,
|
|
periodically re-attempting to execute the file.
|
|
.Pp
|
|
The function
|
|
.Fn exect
|
|
executes a file with the program tracing facilities enabled (see
|
|
.Xr ptrace 2 ) .
|
|
.Sh RETURN VALUES
|
|
If any of the
|
|
.Xr exec
|
|
functions returns, an error will have occurred.
|
|
The return value is \-1, and the global variable
|
|
.Va errno
|
|
will be set to indicate the error.
|
|
.Sh FILES
|
|
.Bl -tag -width /bin/sh - compact
|
|
.It Pa /bin/sh
|
|
The shell.
|
|
.El
|
|
.Sh ERRORS
|
|
.Fn Execl ,
|
|
.Fn execle ,
|
|
.Fn execlp
|
|
and
|
|
.Fn execvp
|
|
may fail and set
|
|
.Va errno
|
|
for any of the errors specified for the library functions
|
|
.Xr execve 2
|
|
and
|
|
.Xr malloc 3 .
|
|
.Pp
|
|
.Fn Exect
|
|
and
|
|
.Fn execv
|
|
may fail and set
|
|
.Va errno
|
|
for any of the errors specified for the library function
|
|
.Xr execve 2 .
|
|
.Sh SEE ALSO
|
|
.Xr sh 1 ,
|
|
.Xr execve 2 ,
|
|
.Xr fork 2 ,
|
|
.Xr trace 2 ,
|
|
.Xr environ 7 ,
|
|
.Xr ptrace 2 ,
|
|
.Xr environ 7 ,
|
|
.Sh COMPATIBILITY
|
|
Historically, the default path for the
|
|
.Fn execlp
|
|
and
|
|
.Fn execvp
|
|
functions was
|
|
.Dq Pa :/bin:/usr/bin .
|
|
This was changed to place the current directory last to enhance system
|
|
security.
|
|
.Pp
|
|
The behavior of
|
|
.Fn execlp
|
|
and
|
|
.Fn execvp
|
|
when errors occur while attempting to execute the file is historic
|
|
practice, but has not traditionally been documented and is not specified
|
|
by the
|
|
.Tn POSIX
|
|
standard.
|
|
.Pp
|
|
Traditionally, the functions
|
|
.Fn execlp
|
|
and
|
|
.Fn execvp
|
|
ignored all errors except for the ones described above and
|
|
.Er ENOMEM
|
|
and
|
|
.Er E2BIG ,
|
|
upon which they returned.
|
|
They now return if any error other than the ones described above occurs.
|
|
.Sh STANDARDS
|
|
.Fn Execl ,
|
|
.Fn execv ,
|
|
.Fn execle ,
|
|
.Fn execlp
|
|
and
|
|
.Fn execvp
|
|
conform to
|
|
.St -p1003.1-88 .
|